1. Field of the Invention
The present invention relates to a communication system, and more specifically, to an apparatus and a related method for tracking a sampling clock of a multi-carrier communication system.
2. Description of the Prior Art
As is well known in the art, a multi-carrier communication system utilizes a plurality of sub-carriers to modulate predetermined transmitted data, then proceeds to transmit the modulated data to a receiver in the form of a continuous data flow. At this time, the receiver samples the above-mentioned continuous data flow utilizing a sampling clock. A phase shift may exist between the received symbol generated by the receiver and the original transmitted data transmitted by the transmitter. This is apparent when the frequency of the sampling clock shifts by a small offset. This phase shift may cause inter-carrier interference (ICI) regarding the received symbol.
A multi-carrier communication system compensates the above-mentioned N received symbols by estimating a sampling clock offset which makes use of pilot symbols. The sampling clock offset is estimated according to the received symbol R and a predetermined data X corresponding to the pilot symbol to eliminate the error caused by the offset.
Please refer to the following equation of the received symbol R in terms of the predetermined data X and other variables:
                              R                      i            ,            j            ,            k                          =                                            ⅇ                                                -                  j2π                                ⁢                                                                  ⁢                                  k                  N                                ⁢                                  τ                                      i                    ,                    j                                                                        ·                          ⅇ                              jψ                                  i                  ,                  j                                                      ·                          H                              j                ,                k                                      ·                          X                              i                ,                j                ,                k                                              +                      N                          i              ,              j              ,              k                                                          equation        ⁢                                  ⁢                  (          1          )                    
Ri,j,k denotes a received symbol transmitted by a kth sub-carrier within a jth band during a ith time period. τi,j denotes a phase difference resulting from a sampling clock offset. ψi,j denotes a carrier phase shift. H denotes a channel estimation value. Ni,j,k denotes a noise signal in the channel.
According to the related art, estimation of the sampling clock offset τi,j is necessary in order to eliminate errors concealed in the received symbol R. However, the receiver must perform a large number of computations regarding the carrier phase shift ψi,j, the channel estimation value H, and the noise signal Ni,j,k, to obtain the sampling clock offset τi,j. Unfortunately, a great deal of resources is consumed during the above-mentioned computation processes.